The invention relates to a method for determining the rigidity of a drivetrain for linear movement of a machine component along a linear guide of a machine, in particular of a machine tool or a production machine, wherein the drivetrain comprises a motor with a motor-measuring system, wherein the linear guide is assigned a length-measuring system for determining the position of the machine component and wherein the machine comprises a numerical controller for closed-loop control of the movement of the machine component.
The invention further relates to a numerical controller and to a machine for carrying out the method.
The objective pursued by manufacturers of machines, especially of machine tools and production machines, is that all machines of a series have the same mechatronic characteristics. Discrepancies are as a rule an indication of lack of quality and must therefore be detected at an early stage.
The operator of a machine would like to insure that, where possible, the machine exhibits the same mechatronic characteristics during its lifetime as it had when it was delivered. Discrepancies can be caused by the failure of components for example and can have downtime as a consequence or, with a machine tool, can lead to low-quality workpieces.
Knowledge of the mechatronic characteristics of the machine is of decisive importance for both the manufacturer and the operator of the machine. It is therefore not surprising that a plurality of tests, by means of which the mechatronic characteristics of a machine can be detected or checked, is known. Examples of said tests are those relating to the positional accuracy of a tool, relating to the friction or relating to the vibration behavior of a machine. As a rule these tests require highly precise and therefore accordingly high-cost measurement equipment to carry out the corresponding measurements.
Carrying out condition monitoring for a machine is known from publication EP2690513A1, in which a dynamic model of the machine is provided and subsequently a frequency analysis is carried out for the machine to determine the values of model parameters. In this way spring stiffnesses of drivetrains of the machine can be established.
A machine diagnosis method and also a facility are known from DE 10 2008 064 391 A1, by means of which a diagnosis of a state or degree of damage such as e.g. the wear of a part or an increase in the working resistance of a machine tool or of an industrial machine can be created. In this process a drive element is moved by a closed-loop position control facility in a predetermined way and the position of the drive element is measured directly by means of a first sensor and measured indirectly by a second sensor detecting the rotational position of a servo motor driving the drive element. On the basis of the difference between the sensor signals an elastic deformation of the drive element is established and, based thereon, information about the state of the machine is built up.